In a medium saucepan, heat the butter over medium-low heat until melted. Add the flour and stir until smooth. Continue cooking until the mixture turns a light, golden sandy color, about 6 to 7 minutes. Meanwhile, heat the milk in a separate pan until just about to boil. Add the hot milk to the butter mixture 1/2 cup at a time, whisking continuously until very smooth. Bring to a boil. Cook 10 minutes, stirring constantly, then remove from heat. Add white cheddar, parmesan and gruyere cheese and whisk until smooth. Season with salt and pepper to taste. Stir in chopped lobster meat and cooked macaroni. Put mixture in ceramic dish and top with mozzarella cheese. Bake at 375 for 10-15 minutes until cheese is browned.